A millimeter wave band corresponding to 57 to 66 GHz may ease a worldwide shortage of frequency resources.
A millimeter wave has unique properties of a short wavelength, a high frequency, a wideband, a large amount of exchange with atmospheric components, and the like. The millimeter wave has merits of a high data transmission rate obtained by using an ultra wideband, a high resistance against interference in proximity due to a high straightness, an excellent security, an easiness of reusing a frequency, and the like. A short wavelength of the millimeter wave may enable various devices to be miniaturized and less weighted.
In contrast, the millimeter wave has demerits of a short propagation length due to an absorption by an oxygen molecule and due to a phenomenon of rain attenuation, and a line of sight may be secured due to a characteristic of straightness.
To make up for the demerits of the millimeter wave, a directional antenna may be used. The directional antenna may concentrate power in a predetermined direction to enhance an efficiency of an antenna gain, thereby extending a communication range. However, even though the directional antenna is used, when the line of sight is not secured, an attenuation loss of a signal may be great due to a transmission length of the signal, a reflection of the signal, and a penetration through a barrier of the signal.
Accordingly, a technology may be used to perform a communication while minimizing an attenuation loss of a signal even when the line of sight is not secured.